The field of the invention relates to engine control systems, including air/fuel and ignition control systems, which provide rapid warm-up of the catalytic converter.
U.S. Pat. No. 5,211,011 describes a system in which fuel delivered to the engine is alternately run rich and then lean while the converter is below a desired temperature, and before closed loop fuel control is commenced. More specifically, an open loop fuel command is forced rich or lean of a desired open loop value. Ignition timing is also retarded until the converter reaches the desired temperature. Thereafter, fuel is adjusted in response to a feedback variable derived from an exhaust gas oxygen sensor.
The inventors herein have recognized numerous problems with the above approaches. For example, a lean open loop fuel command which is intended to result in air/fuel operation slightly lean of stoichiometry may result in air/fuel operation leaner than desired causing rough engine operation and increased emissions. Such leaner than desired operation may occur as the engine and its components age (e.g., slightly clogged fuel injectors). Another problem is that lean operation may reduce engine power which is annoying to the vehicular operator when power is demanded. The deliberate rich perturbation in air/fuel operation of the prior approach may also result in an increase in emissions.